To provide a proper basis of terminology the following standards are used:                (a) Application and service are used synonymously to refer to, for example: Asynchronous Transfer Mode (ATM); Frame Relay (FR); Multiprotocol Label Switching (MPLS); and Internet Protocol (IP).        (b) A link refers to a physical connection (e.g., a copper wire, microwave link, optical fiber cable, etc.) and virtual connections (e.g. an ATM Virtual Path or Virtual Connection, an MPLS tunnel, an optical light path etc.).        (c) A tunnel refers to an aggregate/transport Label Switched Paths (LSPs) in MPLS networks.        (d) Nodes are classified into access/edge nodes, re-routing/core nodes, and backbone nodes depending on the role they play in setting up the connection. The access/edge node originates the connections and performs route computation and network level connection admission control functions. The re-routing node performs similar functions as the access node after a failure notification and when connection re-routing is required. The access and re-rerouting nodes are usually the same in simple flat networks, but may be different in hierarchical or multi-domain networks or when fast re-routing methods are employed. The backbone node performs nodal connection admission control and resource allocation functions on connection setup and sends a connection release message to the re-routing node upon failure detection. In practice, the same node may play all the above roles for different connections. For simplicity, the terms access nodes, edge node and re-routing node are used synonymously throughout.        (e) IP/MPLS Quality of Service (QoS) classes used in the present application include: Expedited Forwarding (EF); Assured Forwarding levels (AF4, AF3, AF2, AFT); and Best Effort (BE).        (f) ATM Quality of Service (QoS) classes used in the present application include: Constant Bit Rate (CBR); Real-Time Variable Bit Rate (VBR-rt); Non-Real-Time Variable Bit Rate (VBR-nrt); and Unspecified Bit Rate (UBR).        
The ATM domain-based re-routing standard describes procedures for re-routing permanent and switched connections at the network/domain edge upon failures. In current ATM networks, upon link failure, all connections have the same priority for re-routing. Therefore, release messages are sent randomly without particular sequence considerations. MPLS networks employ similar methods. In particular, upon link failure MPLS release/failure messages are sent by the core node (termed Label Switch Routers) to the access node (termed Label Edge Routers) or to a node closer to the failure (including the node detecting the failure) for employing one of the re-routing/local repair methods.
Recently, the ATM Forum has proposed to optionally signal the call processing priority when connection is first established. This will enable a service provider to give preferential access to call processing resources for higher priority connections, which takes place during connection setup, clearing and re-routing time. Similarly, the current IETF MPLS standard drafts provide methods for optional signaling of connections set-up and holding priorities, which could be used to provide preferential access to network resources in case of congestion or failure.
However, there is a need for recovery methods that (a) can be policy driven to determine connection re-routing priority in networks where call processing priority is not signaled; (b) can modify the re-routing priority on the basis of configured policies; (c) can modify the re-routing priority adaptively on the basis of dynamic network conditions and/or (d) can schedule or pace the release messages to ensure that priority connections have first access to available network resources and optimal route selection.